The phosphoinositide 3-kinases (PI3Ks) constitute a family of lipid kinases involved in the regulation of a network of signal transduction pathways that control a range of cellular processes. PI3Ks are classified into three distinct subfamilies, named class I, II, and III based upon their substrate specificities. Class IA PI3Ks possess a p110α, p110β, or p110δ catalytic subunit complexed with one of three regulatory subunits, p85α, p85β or p55δ. Class IA PI3Ks are activated by receptor tyrosine kinases, antigen receptors, G-protein coupled receptors (GPCRs), and cytokine receptors. The class IA PI3Ks primarily generate phosphatidylinositol-3,4,5-triphosphate (PI(3,4,5)P3), a second messenger that activates the downstream target AKT. The consequences of biological activation of AKT include tumour cell progression, proliferation, survival and growth, and there is significant evidence suggesting that the PI3K/AKT pathway is dysregulated in many human cancers. Additionally, PI3K activity has been implicated in endocrinology, cardiovascular disease, immune disorders and inflammation. It has been established that PI3K-p110δ plays a critical role in the recruitment and activation of immune and inflammatory cells. PI3K-p110δ is also upregulated in a number of human tumours and plays a key role in tumour cell proliferation and survival.
Compounds which are able to modulate p110δ activity have important therapeutic potential in cancer and immune and inflammatory disorders.
WO2006/046035 describes fused pyrimidines, which have activity as inhibitors of PI3K. The compounds disclosed therein exhibit selectivity for class Ia PI3Ks, notably p110δ.